Cleo is Tony Starks biological daughter, neither of them know this in the beginning of the story, set post season 3 of H2o, story starts set in 2011.
Cleo applied to several universities to study marine biology, this includes MIT (USA), Australian national University, Caltech (USA), University of Oxford (United Kingdom), to name a few, she gets into about half of them and is waitlisted on a quarter, she chooses to go to Caltech with a partial scholarship which cover housing and half of her tuition.
Pre season 3 Emma decides in preparation for her move she would go to the moon pool during a full moon and give up her tail and magic, this causes her and Rikki to break off their friendship since Rikki can’t understand why Emma would want to do this, Cleo stayed in touch with Emma for a while but they naturally drifted apart mid-season 3.
Post season 3 Rikki continues managing Rikki’s Cafe and with money she’s been saving up she starts attending night classes at the local community college for a business degree, Rikki and Cleo have bonded a lot more post season 3 (Sapphic relationship maybe??).
Cleo and Lewis’s relationship is rocky at the moment, being long distant and both of them being busy starting this new stage of their lives means they don’t have much time for each other and when they eventually make time they mostly talk about how much they miss each other and how disconnected they feel from each other. After a long talk though they decide to break up but since neither of them can picture life without the other they stay friends which helps take the pressure off their interactions.
Although in contrast to Lewis and Cleo failing relationship Rikki and Cleo make appoint to meet at least once a month at Mako Island (Cleo has gotten a lot faster at swimming) and they talk online everyday (sometimes the conversations are short but their still important), Cleo also makes a point to call home once a week to talk with her father and Kim.
Speaking of Kim, once Cleo moved out the twos relationship improved drastically by not being in each other’s space so often it was a lot easier to talk without arguing and constantly snapping at each other.
Bella will not be a prominent character but what happened to her post season 3 is that she went on to pursue her music career and travel around Australia performing in local cafés and small venues kind of like Lane and her band did in Gilmore Girls.
Cleo struggled growing up with people not taking her seriously and when she became friends with Emma she would often be referred to as the dumb one of the two.
Rikki and Zane stay business partners and platonic after their break up in season 3.
Cleo was adopted as a baby by the Setori’s since they were having trouble conceiving kid naturally, her parents explained she was adopted when they suddenly become pregnant with Kim and Cleo was asking questions about why there aren’t any pictures of her mum pregnant with her.